The present disclosure generally relates to electromachining apparatuses and processes, and more particularly, to an electromachining apparatus and process configured for providing both roughing and finishing operations.
A large amount of time is spent in machining different types of metal components for commercial and industrial usage. The amount of time is generally dependent on the material being machined and the machining method used. One method used frequently for complex components, particularly those with contours, is milling. This can take a substantial amount of the overall component processing time. For the most demanding applications, carbide cutters are typically utilized. Other methods include electrodischarge machining (EDM) which is widely used for machining complex parts and dies and molds.
EDM is a process in which an electrically conductive metal workpiece is shaped by removing material through melting or vaporization by electrical sparks and arcs. The spark discharge and transient arc are produced by applying controlled pulsed direct current between the workpiece (typically anodic or positively charged) and the tool or electrode (typically the cathode or negatively charged). The end of the electrode and the workpiece are separated by a spark gap generally from about 0.01 millimeters to about 0.50 millimeters, and are immersed in or flooded by a dielectric fluid. The DC voltage enables a spark discharge charge or transient arc to pass between the tool and the workpiece. Each spark and/or arc produces enough heat to melt or vaporize a small quantity of the workpiece, thereby leaving a tiny pit or crater in the work surface. The cutting pattern of the electrode is usually computer numerically controlled (CNC) whereby servomotors control the relative positions of the electrode and workpiece. The servomotors are controlled using relatively complex and often proprietary control algorithms to control the spark discharge and control gap between the tool & workpiece. By immersing the electrode and the workpiece in the dielectric fluid, a plasma channel can be established between the tool and workpiece to initiate the spark discharge. The dielectric fluid also keeps the machined area cooled and the removes the machining debris. An EDM apparatus typically includes one or more electrodes for conducting electrical discharges between the apparatus and the part.
One drawback to current EDM processes is that it is a relatively slow process, especially when several distinct features need to be machined into a workpiece. This is particularly so in the aircraft engine industry where electrical discharge machining is widely used for machining various features into aircraft engine parts. Because of this as well as for other reasons, EDM is generally used for fine finishing and not for roughing operations where large quantities of material are removed.
High-speed electroerosion processes have been recently developed that uses spark/arc discharges through an electrolytic medium. Although these processes utilize an electrolyte, it is typically much weaker than those electrolytes used in an electrochemical machining (ECM) processes, and the primary material removal mechanism is thermal via spark/arc discharge. The high speed electroerosion process must have relative movement between the tool and workpiece, and this process uses a different control method relative to EDM.
It would be desirable to have an electromachining apparatus and process that efficiently provides both high speed roughing using the high speed electroerosion process and finishing of the workpiece by EDM.